David Amess is Conservative MP for Southend West and a member of the British Parliamentary Committee for Iran Freedom

It emerged last week that oil giant BP recently instructed its European operations not to provide fuel to Iranian planes following the adoption of international sanctions targeting the Islamic Republic's gasoline industry over its nuclear proliferation. That's a positive step. But in order to bring an end to Iran's nuclear weapons programme without the prospect of a war, more aggressive measures are needed now by the British Government and our allies.

Foreign Secretary William Hague said recently that Britain had worked hard with other nations on proposals to secure new United Nations and European action to reinforce diplomatic pressure on Iran.

But the hardline Iranian President has described the most recent bout of sanctions as a "pathetic" act, and Iranian military commanders have warned they would reciprocate any hostile action by the West.

With Iran continuing to enrich uranium needed for a nuclear bomb to higher levels, Mr. Hague is correct to want to increase pressure on Tehran; but ultimately the policy of tougher sanctions will only work if the West firmly abandons the engagement track with the mullahs and instead looks to support the Iranian pro-democracy forces.

Unlike Iraq, Iran has an organised opposition movement. Last year, we witnessed millions taking to the streets repeatedly demanding regime change. What began as a protest at the results of Iran's rigged elections last summer quickly turned into a movement to topple the country's religious leaders. It is, frankly, to the West's shame that it kept virtually mute as Revolutionary Guards and members of the paramilitary Bassij beat and killed hundreds of opposition supporters. If instead it had threatened to sever ties with the regime over the crackdown, the mullahs would have become wary of their actions and Iranians would have been encouraged to challenge the regime with even greater determination.

Exiled opposition leader Mrs Maryam Rajavi, who heads the National Council of Resistance of Iran (NCRI), has made clear that her coalition supports a democratic, secular and non-nuclear Iran which respects human rights and lives in peace with its neighbours.

Last month the opposition held a major rally in Paris, drawing tens of thousands who all supported domestic regime change without the need for foreign military intervention. Prominent conservatives such as former Spanish Prime Minister José María Aznar and European Parliament Vice President Alejo Vidal-Quadras turned up to support the option of democratic change by the Iranian people and their Resistance movement.

Mr. Aznar noted that "the Iranian people deserve a government that is not based on brutal repression. … They need and deserve a change of regime in Iran".

John Bolton, the former US ambassador to the UN, said at the rally the US government must adopt an "active regime change policy", which "will not stand in the way of legitimate opposition groups".

The same holds true for Britain and the European Union. Mrs. Rajavi says rightly that the latest international sanctions are necessary, but insufficient.

In order to avert the prospect of a war with Iran, we must now actively support the organised Iranian opposition and cut all economic and diplomatic ties with the regime so that the people there are able to build on the momentum of the anti-government protests and bring about regime change.